1. Field of the Invention
The present invention relates to a method of supporting and/or conveying a plate with fluid without physical contact. It is especially useful for supporting and/or conveying plates such as a silicone wafer or a floppy disc whose surface should be protected from minute scratches or contamination without physical contact with fluids such as air, and conveying them, if necessary, in the floating state.
2. Description of the Prior Art
The inventor of the present invention proposed in Japanese Pat. No. 40343/1976 a method of supporting a plate with fluid without physical contact, in which a suction pipe, and a delivery pipe which has an orifice near its delivery opening, are assembled as the openings of the suction pipe and of the delivery pipe face the same direction, and a fluid is inhaled in the suction pipe and at the same time a fluid is delivered from the orifice to support a plate near the openings without physical contact.
More particularly, as shown in FIGS. 1 and 2, a suction pipe 1p, and a delivery pipe 3p provided with an orifice 2p near the opening, are assembled such that openings 4p, 5p of both pipes located above plate 8 face the same direction, and a fluid 6 such as air is inhaled in the suction pipe 1 and at the same time a fluid 7 such as air is delivered from the orifice 2p as a jet flow, the negative pressure at the suction pipe 1p and the delivery pressure at the delivery pipe 3p being adjusted in proportion to the weight of the plate to be supported. Then, the plate 8 can be supported in the air without physical contact, keeping the distance between the openings 4p, 5p and the flat plate 8 constant and in the range of about 0.5 mm to several mm. The plate 8 can be conveyed horizontally, keeping the distance h, by applying a little force to the horizontal direction. In the drawing, 9p and 10p are ducts.
Where the vertical delivery opening 5p is extended to a substantially perpendicular direction (horizontal) to the flow of fluid in the delivery pipe 3p to form a flat surface 11p, and a plate 8 is brought under the opening 5p (FIG. 3), when the current speed of fluid 7 in the pipe 3p is constant, and when the distance of the gap h between the flat surface 11p and the upper face of plate 8 decreases, the current speed of fluid in the gap h increases, and the static pressure at the gap h decreases in accordance with Bernoulli's theorem. When this static pressure decreases to beneath atmospheric pressure and the product of this negative pressure and the area of the gap reaches to balance with the weight of plate 8, the plate 8 floats in the air without physical contact, with only a delivery pipe and without a suction pipe.
In the inventor's prior invention disclosed in Japanese Patent Application No. 71950/1985, the inventor has disclosed the test results of this theory, in which a plate was supported and/or conveyed with fluid without physical contact, by providing a flat surface 11p extending at opening 5p of a delivery pipe 3p to a substantially perpendicular direction to the flow direction of fluid 7 in the pipe 3p, moving the opening 5p near a plate 8, and delivering fluid 7 from delivery pipe 3p, as shown in FIGS. 3 and 4.